Messages in this thread Patch in this message |  | | From | Jiakai Xu <> | | Subject | [PATCH v3] PM: sleep: Use complete() in device_pm_sleep_init() and skip no_pm devices in dpm_wait() | | Date | Sat, 23 May 2026 02:23:14 +0000 |
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Replace complete_all() with complete() in device_pm_sleep_init() to allow it to be called in atomic contexts without triggering a false-positive WARNING from lockdep_assert_RT_in_threaded_ctx() when CONFIG_PROVE_RAW_LOCK_NESTING is enabled.
device_pm_sleep_init() may be called during device initialization while holding a raw_spinlock (e.g., from within device_initialize()), and complete_all() is unsafe in atomic contexts on PREEMPT_RT kernels. complete(), which is safe to call from any context, is sufficient here.
complete_all() sets the completion count to UINT_MAX/2 (permanently signaled), while complete() increments it by 1. Since no threads can be waiting during device initialization, both are functionally equivalent. The completion is always reinitialized via reinit_completion() in dpm_clear_async_state() before each suspend/resume cycle.
However, changing to complete() introduces a potential deadlock for devices with no PM support (dev->power.no_pm = true). Such devices are never added to the dpm_list and never go through dpm_clear_async_state(), so their completion is never reinitialized. A parent device waiting on a no_pm child across multiple suspend phases would consume the single-use token in the first phase and block forever in the second.
Fix this by adding an early return in dpm_wait() when dev->power.no_pm is set, since no_pm devices do not participate in system suspend/resume.
Fixes: 152e1d592071 ("PM: Prevent waiting forever on asynchronous resume after failing suspend") Signed-off-by: Jiakai Xu <xujiakai24@mails.ucas.ac.cn> --- V1 -> V2: - Updated dpm_wait() to skip devices with no PM support, as suggested by Rafael J. Wysocki.
V2 -> V3: - Revised commit message to clarify that the lockdep warning originates from device_pm_sleep_init() called in atomic context, not from device_pm_remove(). No code changes relative to v2. --- drivers/base/power/main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index e1b550664bab..ed48c292f575 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -115,7 +115,7 @@ void device_pm_sleep_init(struct device *dev) dev->power.is_noirq_suspended = false; dev->power.is_late_suspended = false; init_completion(&dev->power.completion); - complete_all(&dev->power.completion); + complete(&dev->power.completion); dev->power.wakeup = NULL; INIT_LIST_HEAD(&dev->power.entry); } @@ -252,6 +252,10 @@ static void dpm_wait(struct device *dev, bool async) if (!dev) return; + /* Devices with no PM support don't use the completion. */ + if (dev->power.no_pm) + return; + if (async || (pm_async_enabled && dev->power.async_suspend)) wait_for_completion(&dev->power.completion); } -- 2.34.1
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